跨线程操作无效:控制从创建它的线程以外的线程访问的“textBox1”
本文关键字:线程 访问 textBox1 创建 无效 操作 控制 | 更新日期: 2023-09-27 18:35:25
我想使用 UART 将温度值从微控制器发送到 C# 接口并在Label.Content
上显示温度。这是我的微控制器代码:
while(1) {
key_scan(); // get value of temp
if (Usart_Data_Ready())
{
while(temperature[i]!=0)
{
if(temperature[i]!=' ')
{
Usart_Write(temperature[i]);
Delay_ms(1000);
}
i = i + 1;
}
i =0;
Delay_ms(2000);
}
}
我的 C# 代码是:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
txt += serialPort1.ReadExisting().ToString();
textBox1.Text = txt.ToString();
}
但那里出现了例外"跨线程操作无效:控制从创建它的线程以外的线程访问的'textBox1'"请告诉我如何从我的微控制器获取温度串并删除此错误!
serialPort1_DataReceived
方法中接收的数据来自 UI 线程以外的另一个线程上下文,这就是您看到此错误的原因.
若要解决此问题,必须使用 MSDN 文章中所述的调度程序:
如何:对 Windows 窗体控件进行线程安全调用
因此,不要直接在 serialport1_DataReceived
方法中设置 text 属性,而是使用以下模式:
delegate void SetTextCallback(string text);
private void SetText(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (this.textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
this.textBox1.Text = text;
}
}
所以在你的情况下:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
txt += serialPort1.ReadExisting().ToString();
SetText(txt.ToString());
}
我不知道
这是否足够好,但我做了一个静态的ThreadHelperClass类并实现如下。现在我可以轻松设置各种控件的文本属性,而无需太多编码。
public static class ThreadHelperClass
{
delegate void SetTextCallback(Form f, Control ctrl, string text);
/// <summary>
/// Set text property of various controls
/// </summary>
/// <param name="form">The calling form</param>
/// <param name="ctrl"></param>
/// <param name="text"></param>
public static void SetText(Form form, Control ctrl, string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (ctrl.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
form.Invoke(d, new object[] { form, ctrl, text });
}
else
{
ctrl.Text = text;
}
}
}
使用代码:
private void btnTestThread_Click(object sender, EventArgs e)
{
Thread demoThread =
new Thread(new ThreadStart(this.ThreadProcSafe));
demoThread.Start();
}
// This method is executed on the worker thread and makes
// a thread-safe call on the TextBox control.
private void ThreadProcSafe()
{
ThreadHelperClass.SetText(this, textBox1, "This text was set safely.");
ThreadHelperClass.SetText(this, textBox2, "another text was set safely.");
}
你可以简单地做到这一点。
TextBox.CheckForIllegalCrossThreadCalls = false;
使用以下扩展并传递如下操作:
_frmx.PerformSafely(() => _frmx.Show());
_frmx.PerformSafely(() => _frmx.Location = new Point(x,y));
扩展类:
public static class CrossThreadExtensions
{
public static void PerformSafely(this Control target, Action action)
{
if (target.InvokeRequired)
{
target.Invoke(action);
}
else
{
action();
}
}
public static void PerformSafely<T1>(this Control target, Action<T1> action,T1 parameter)
{
if (target.InvokeRequired)
{
target.Invoke(action, parameter);
}
else
{
action(parameter);
}
}
public static void PerformSafely<T1,T2>(this Control target, Action<T1,T2> action, T1 p1,T2 p2)
{
if (target.InvokeRequired)
{
target.Invoke(action, p1,p2);
}
else
{
action(p1,p2);
}
}
}
与之前的答案相同,但是一个非常简短的添加,允许使用所有 Control 属性而不会有跨线程调用异常。
帮助程序方法
/// <summary>
/// Helper method to determin if invoke required, if so will rerun method on correct thread.
/// if not do nothing.
/// </summary>
/// <param name="c">Control that might require invoking</param>
/// <param name="a">action to preform on control thread if so.</param>
/// <returns>true if invoke required</returns>
public bool ControlInvokeRequired(Control c,Action a)
{
if (c.InvokeRequired) c.Invoke(new MethodInvoker(delegate { a(); }));
else return false;
return true;
}
示例用法
// usage on textbox
public void UpdateTextBox1(String text)
{
//Check if invoke requied if so return - as i will be recalled in correct thread
if (ControlInvokeRequired(textBox1, () => UpdateTextBox1(text))) return;
textBox1.Text = ellapsed;
}
//Or any control
public void UpdateControl(Color c,String s)
{
//Check if invoke requied if so return - as i will be recalled in correct thread
if (ControlInvokeRequired(myControl, () => UpdateControl(c,s))) return;
myControl.Text = s;
myControl.BackColor = c;
}
使用共享容器在线程之间传输数据。